Only a short distance away, you will find Asklipieio, the ancient theatre of Epidavros, one of the most important, best preserved and famous ancient theatres in the world, where, even today, there are plays during the summer, offerning an lifetime experience, during the summer months. http://www.greekfestival.gr/gr/program
From Nafplion, you can easily visit the historic Ancient Mycenae, kingdom of the mythical King Agamemnon. You can walk around the ancient acropolis of Mycenae, visit the tombs ot Atreus and Klitemnistra, and visit the museum, where you can see a variety of ancient findings, jewels, and golden items, from the Mycenean Era.
You should not miss the Roman Baths and the ancient theatre of Argos, one of the oldest theatres of Greece, as well as the acropolis of Ancient Tyrins.
Should you wish to try something different, you can visit the nearby villages and find yourselves in the heart of non-touristic Greece. VIllages like Kefalari with its river, flowing right under a church built on the rocks, or Elliniko with its pyramid, dated 14th century BC.
During the summer months, the numerous beaches of Nafplion make it an ideal destination. You can swim in the beaches of Arvanitia and Karathona, both very close to the center of the town, or visit the beach of Tolo, with its tirquoise waters and fine, white sand, or, a bit further, the beach of Ag. Nikolaos (a.k.a. Kondyli), after the village of Vivari, where you will find an organized beach with the cleanest, clearest waters in the area.